Tandem-bed hydroforming process



July 14, 1953 A, CLARK 2,645,604

TANDEM-BED HYDROFORMING PROCESS Filed Sept. 7. 1949 NAPHTHA IN VEN TOR.

ALFRED CLAR K A TOR/VE YS Patented July 14, 1953 .TANDEM-BED HYDROFORMING PROCESS 7Alfred Clark, Bartlesville, Okla., assignor to Phillips' Petroleum Company,.a corporation of `Delaware Application September 7, 194,9, Serial No. 114,363

.This .invention relates to the conversion of a .low octane number hydrocarbon into a highoctane number motor fuel componentby a process `of hydroforming. Hydroforming is ga term apl.plied-quite generally in the petroleum conversion art and consists essentially of contacting hydrocarbons, 4particularly those boiling substantiallyin the gasoline range, withV ahydroforming catalyst at a .temperature of, Say, S50-1150" VF., apressure of say, 50-500 pounds per square inch gauge, a feed .rate of liquidhydrocarbon of about, 0.2 to about 2 volumes per volume of catalyst, per hour, hydrogen being added to the feed at a rate of say, V50G-500,0 cubic feet per barrel of naphtha. The feed streams are preheated to the initial conversion temperature. No direct heating of the catalyst is employed and, because the conversion is endothermic, the temperature of the hydrocarbons decreases. during their passage through the converter. After an extended period of operation the catalyst activity defcreases due to coke. lay-down Which then-must f be. burned Yolf to restore the catalyst to substan- `tally its4 original activity. Among the catalysts Whichhave been employed vas hydroforming catalysts are ,chromia-alumina and molybdenumoxide-alumina. v v

In one of its embodiments this invention is concerned with a modied hydroforming process in which two catalyst stages are employed as set forth below.

: effluent from the rst stage ,is fractionatedand i the fractionboiling -in 'the fairlyharrow range 22T-232 F. and consisting of about/90% toluene is'reheated and vthen passedto the second stage which is to be maintained at. a. higher pressure than that employed in the first stage.

2. It is also knownin thaart to vhydroform a mixture of virgin andcrackednaphthas in a twostage process-with intermediate reheating of the efuent 'from' the rst Vstage to about l000 F.

before it enters the second stage` They catalysts disclosed include molydenum oxide-alumina and chromia-.alumina. From this prior `art disclosure it appears that these catalysts can be 'employed in both stages of the process.

3. Still further, it has been `prc posed in .the prior art to effect-a two-.stage ,hydroforming witha molybdenum oxide-alumina ,catalyst` in ZClaimS. (Cl. ISB-+49) a rststage and with a chromia-alumina.cata-A lystin asecond `stage with intermediate separation` of product by solvent extraction between lthetwo stages-with reheating and treatment in the `second stage of only the ralinate.

Sinceyin the process set out at (l) above, only a toluene streamis passed to the second stage, it is evident to the present inventor that a highly desirable isomerization of parans can- `not be accomplished in the said second stage.

Furthermore, theV said process, set out at (l) hereof, has the disadvantages that intermediate cooling, fractionation, reheating, and increased pressure in the second zone as well as the attendant equipment and concomitant expense are required.

In the process set out at (2) above, the intermediate reheating of the first stage efuent to a temperature of about 1000'F., is considered by the present inventor to be too high to effect an optimum, paraffin isomerization in the second stage in presence of molybdenum oxide-alumina. Also, said process, set out at (2) hereof, requires highly specic charge stocks but, evidently, does not teach that any combination and order of the catalysts disclosed shall be employed. Furthermore, there is involved the intermediate reheating which, as stated, is considered to be a disadvantage from both optimum operation and Aexpense viewpoints.

The process set forth at (3) above teaches an order of catalysts opposite to that of the process set forth at (l) hereof. Also, the said process set forth at 3) above requires intermediate solvent extraction Aand reheating steps.

From the foregoingA presentation of three prior lart processes in which at least one of the hydroforming reactions appears to be `effected it is evident that4 a simplied operation would be highly desirable.

It is amongthe objects ofthis invention Yto provide a simplied process for the hydroforming of a hydrocarbon.

Also among theobjects of this invention, is to provide a two-stage hydroformingprocess in Which the octane number of ahydrocarbon is materially` increased, Without necessity of intermediate, product separation by fractionation or solvent extraction.

. stage.

Another object of the invention is a two-stage Vhydroforming process which does not require highly specic charging stocks.

Astill furtheiyobject of the invention is a twostage hydroforming process in which the catalysts have a longer activity period because coke formation has been reduced to a minimum.

Another of the several objects of this invention is to provide an improved hydroforming process which while it eliminates certain steps and features of prior art processes which are cumbersome, time consuming and expensive steps nevertheless retains and adds to the advantages thereof which have been derived.

Other objects and advantages are apparent r from this speciiication, the appended claims and the drawing.

According to this invention there is provided a process for the hydroforming of a hydrocarbon in a specific manner which comprises the steps of passing said hydrocarbon into a catalytic conversion zone in which in a rst section the hydrocarbon at a temperature in the range of 900-1l00 F. is contacted with a chromia-alumina catalyst following which it is passed to a second section of said conversion zone directly without any intermediate steps wherein it is contacted at a temperature in the range 800-950 F. with a molybdenum oxidealumina catalyst, the temperature in said second section always being lower than in said first section, to cause in the first section an optimum conversion for the chromiaalumina catalyst and in the second section an optimum conversion of the effluent of the first for the molybdenum oxide-alumina catalyst.

To more fully set forth and to describe the process of the invention reference is made to the .drawing which diagrammatically illustrates the treatment of a hydrocarbon stream effected according to the invention.

A naphtha charge to be hydroformed is admixed with hydrogen and the mixture is preheated to a temperature of about 950-ll00 F. and passed through conduit I into an adiabatic hydroforming zone 2 containing beds of chromiaalumina catalyst 3 supported on trays ll. The charge passes down through hydroformer 2 immediately passing over beds of` molybdenum oxide-alumina catalyst 5 supported on trays 6 and then from the hydroformer through conduit 1. It is to be noted that the charge which has been' contacted with the chromia-alumina catavlyst, immediately and Without any intermediate readily for optimum results in case of each charging stock.

The chromia-alumina catalyst may also contain promoters or stabilizers; such as, beryllium and alkaline earth oxides. These catalysts may be prepared by any method known in the art. The molybdenum oxide-alumina catalyst may contain other promoters or stabilizers; such as, silica, alkali, alkaline earth oxides, vanadia, and tungsten oxide.

AAs stated, the temperature will be in the range 800-1100 F. and that prevailing in the second section of the hydroformer will be lower than that in the first section. Thus good results are obtainable when the temperature of the rst section is about 950 F. to :about 1050 F. and the temperature in the second section is about 930 F. to about 850 F. Optimum parain isomerization is obtained in the second section in this temperature range. Also, in general, the higher the temperature and the more parainic the naphtha used, the larger will be the ratio of chromiaalumina catalyst to molybdenum oxide-alumina catalyst. The molybdenum oxide-alumina catalyst will, in general, occupy 25-75% of the total catalyst space; for general use, about 50% is satisfactory. When the feed is a normal-paraffinic naphtha (low-octane number), the molybdenum oxide-alumina catalyst may be used in excess over the chromia-alumina. When the naphtha feed contains substantial amounts of isoparafns (higher octane number), the chromia-alumina may predominate.

The chromia-alumina catalyst initially contains 5-45% Cr203, most of the remainder being A1203, and the use of l-l0% BeO or MgO being very desirable. The molybdenum oxide-alumina catalyst initially contains 5-30% M003 deposited on alumina; 1-5% S102 may also be present.

Feed rates of 0.5-2 volumes of naphtha per l volume of catalyst per hour can be employed for satisfactory results. f

The quantity of hydrogen can be about 500- 5000 cubic feet per barrel of naphtha.

The pressure can be 50-500 pounds per square inch, preferably 20D-250 pounds per square inch, for good results although pressures higher or even lower may be used.

The immediate treatment of the efuent of the `first section in the .second section tends to avoid substantially any reverse or even adverse reaction which can take place during a cooling, fractionation or separation and reheating steps as employed in the prior art.

The following example is illustrative of actual results obtained employing a tandem catalyst bed or hydroforming zone according to the process of the invention. Run B was on a more naphthenic naphtha than run A. The reactor vessel contained a chromia-beryllia-alumina catalyst in the upper half and a molybdenum oxide-silica-alumina in the lower half. Downow of feed was employed.

Example Run A i B Liquid Space Velocity, Vol./ Feed Feed Catalyst Vol/Hr l l Pressure, Lbs/Sq. In. Gauge 215 244 Average Temperature, F 919 907 Temperature Drop Through the Bed, F 950-861 951-848 Product Yields, Wt. Percent of N aphtha Feed:

Total 100.0 100.0

Properties of 05+ Hydrocarbon:

Research Octane Clear 22.7 66. 7 64. 5 88.5 Motor Octane Clear 28. 2 62. 2 64.8 78. 4 Refractive Index (20 C.) 1. 4307 1. 4400 1. 4411 1. 4580 Bromiue Number 2. 9 3. 4 1.0 3.2

NOTES:

(l) The hydrogen to naphtha ratio was 2500 cubic feet per barrel. (2) A five hour process cycle was employed.

(3) Most of the loss is believed to have been C4 and lighter gases. The coke figure is slightly high due to shortness of run-5 hrs,

The increase in octane number as well as the W percentage of coke are noteworthy in the example.

Reasonable variation and modication are possible within the scope of the foregoing disclosure and the appended claims to the invention the essence of which is that a considerably simplified two-stage hydroforming process which eliminates all the prior art cooling, fractionation, solvent extraction, reheating and pressure increasing steps and provides an optimum catalyst sequence wherein the entire charge is optionally converted in each Zone with longer catalyst life (less coking) and therefore the saving of time and expense has been set forth and described.

I claim:

1. The hydroforming of a naphtha which comprises passing said naphtha at a temperature in the range 950-1050 F. and a pressure in the range of 200 to 250 pounds per square inch gage into contact with a chroznia-alumina catalyst in a first stage and then passing the eiiuent from said stage immediately and without any additional intermediate step directly into contact with a molybdenum oxide-alumina catalyst under hydroforming conditions in a second stage in which the temperature prevailing is lower than that in said first stage and is in the range 850930 F. and the pressure in said second stage is substantially the same as in said rst stage.

2. The hydroforming of a naphtha which comprises passing said naphtha in admixture with hydrogen, and which admixture comprises the sole feed to the process, at a temperature in the range 900-1l00 F. and a pressure in the range of 200 to 250 pounds per square inch gage into contact with a chromia-alumina catalyst in a first stage and then passing the eiiluent from said stage immediately and without any additional intermediate step directly into contact with molybdenum oxide-alumina catalyst under hydroforming conditions in a second stage in which the temperature prevailing is lower than in said first stage and is in the range S-930 F.; the pressure in said second stage being substantially the same as in the rst said stage and withdrawing from second stage the sole eiuent of the process.

ALFRED CLARK.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,955,297 Jennings Apr. 17, 1934 2,293,759 Penisten Aug. 25, 1942 2,322,622 Fischer et al June 22, 1943 2,345,575 Burk et al Apr. 4, 1944 2,348,624 Hillman May 9, 1944 2,349,812 Day et al May 30, 1944 2,349,826 Layng May 30, 1944 2,378,209 Fuller et al June l2, 1945 2,404,902 Claussen et al July 30, 1946 2,417,308 Lee Mar. 11, 1947 

1. THE HYDROFORMING OF A NAPHTHA WHICH COMPRISES PASSING SAID NAPHTHA AT A TEMPERATURE IN THE RANGE 950*-1050* F. AND A PRESSURE IN THE RANGE OF 200 TO 250 POUNDS PER SQUARE INCH GAGE INTO CONTACT WITH A CHROMIA-ALUMINA CATALYST IN A FIRST STAGE AND THEN PASSING THE EFFLUENT FROM SAID STAGE IMMEDIATELY AND WITHOUT ANY ADDITIONAL INTERMEDIATE STEP DIRECTLY INTO CONTACT WITH A MOLYBDENUM OXIDE-ALUMINA CATALYST UNDER HYDROFORMING CONDITIONS IN A SECOND STAGE IN WHICH THE TEMPERATURE PREVAILING IS LOWER THAN THAT IN SAID FIRST STAGE AND IS IN THE RANGE 850*-930* F. AND THE PRESSURE IN SAID SECOND STAGE IS SUBSTANTIALLY THE SAME AS IN SAID FIRST STAGE. 